Study On Measuring Method And Characteristics Of Friction Behavior In Continuous Casting Mould

The mould friction is the important factor to reflect the lubrication condition between the mould and strand,which not only influences the surface quality of slab and the stable production,but also has the great application potential on estimating the lubrication effect of powders,predicting the breakout and improving the slab quality.Mould oscillation plays an important role in the continuous casting.In recent years,the hydraulic oscillation is developed and has been widely applied as a driven equipment of mould oscillation.With the development of hydraulic oscillation,the research on the MDF measurement methods and the frictional characteristics with hydraulic oscillators has theoretical and practical importance for further improving the casting speed,insuring the slab quality and preventing the breakout.The aim of the dissertation is to study the measuring method and character the mould frictional behavior between the strand surface and mould.With the hydraulic oscillator of continuous slab caster two measuring methods of MDF have been developed:pressure method for detecting the transient MDF and frictional work method for average MDF.The systematical experimental investigations for frictional characteristics in the mould have been analyzed in terms of time domain and frequency domain,as well as their influencing factors. The MDF measurement is realized by detecting the displacements and pressures of the hydraulic oscillators and the calculating model is developed.Meanwhile,the same measuring signals:displacement and pressure are used to measure and estimate the oscillation state of hydraulic oscillator.Firstly,through measuring and calculating the hydraulic cylinder displacement,pressure and other parameters,the dissertation tries to explore the method to detect and estimate the oscillation of hydraulic oscillator.The variations of displacement differences,phase differences are analyzed with various frequency,amplitude and deviation angle.Especially, the synchronization and the dynamic characteristics of the driving force of left and right cylinders are evaluated.The result indicates that the hydraulic oscillators have high oscillating precision,which provides the foundation for the accurate detection and calculation of MDF.Secondly,according to the oscillation characters of the hydraulic oscillator,the loading state of mould is analyzed,the loading model is built and the theoretical basis and the general idea of pressure method are determined to detect the transient friction.Based on the work above,the real friction status between the mould and slab is detected in a plant trial.The periodical variations and characteristics of mould friction are researched.In addition,the results of transient MDF are compared and analyzed under different oscillation modes, control models as well as the normal and the abnormal conditions.This study provides the experimental basis for the transient characteristics of mould friction.Thirdly,based on the loading analyses of mould oscillator and the characters of sinusoidal mode,the theoretical model for frictional work method is built to characterize the whole frictional behavior in mould.With the help of Artificial Neural Network,the equivalent damping of oscillation is forecasted and the thought is established to detect and calculate the average MDF.According to the monitored data of average MDF,the effects of oscillation synchronization on MDF are analyzed and discussed as well as the different oscillation modes and other conditions.Further,the average characters of MDF are studied.Finally,according to the transient MDF data by pressure method,using Fast Fourier Transformation(FFT) analysis,MDF in the time domain is transformed into the signal in frequency domain with the help of frequency spectral analysis.The fundamental frequency and harmonic frequency as well as the amplitudes of MDF signal in the frequency domain are investigated and the frequency domain characteristics of MDF are discussed.In addition,by using the frequency domain analyzing method,the oscillation state and dynamic characteristics of hydraulic oscillator are also studied preliminarily.The results show that the frequency characteristics of MDF have good sensitivity on the variation of the operational parameters and can reflect the abnormal lubrication information between strand and mould. The study for the frequency domain characteristics of friction provides a new idea for online detection of MDF.